This invention relates to rotary wing aircrafts and, more particularly, to a retaining assembly for a pitch control system of a rotary wing aircraft.
Conventional rotary wing aircrafts, such as helicopters for example, generally include a tail rotor configured to create aerodynamic thrust to compensate for the rotor torque generated by a main rotor. The tail rotor includes a tail rotor hub having multiple rotor blades mounted thereto. Arranged adjacent the tail rotor is a pitch control system including a pitch beam attached to an end of the pitch change shaft. The pitch beam has multiple arms, each of which is coupled to a corresponding tail rotor blade through a pitch linkage. A dual stage servo provides axial movement of the pitch change shaft relative to a tail rotor hub, thereby manipulating the rotational displacement of the rotor blades.
A retaining assembly including a torque reacting washer and a retaining nut, is used to prevent linear movement of the pitch beam relative to the pitch change shaft. Self-locking inserts of the retaining nut provide a first locking feature and locking fasteners configured to mechanically couple the retaining nut to the washer provide a second locking feature of the retaining assembly. Despite both of these locking features, potential for improper installation of the retaining assembly exists, for example by improperly engaging the washer with the pitch change shaft. As a result of improper installation, vibrations generated by the rotation of the tail rotor may cause an improperly torqued retaining assembly to loosen or ultimately separate from the pitch change shaft.